1. Technical Field
This invention relates to a method for preparing functional thin films and the thin films, and more particularly, to a method for preparing silicon or silicon compound thin films for use in TFT, solar batteries, magnetic heads and thermal heads, and the silicon or silicon compound thin films obtained thereby.
2. Background Art
In the recent years, semiconductor products using silicon are more diversified. A variety of products were developed and have been used in practice. Among others, applied products of silicon or silicon compound thin films draw engineers' attention as being applicable to thin film transistors (TFT), charge transfer devices (CCD), solar batteries, organic EL devices, magnetic heads and thermal heads.
Of the applied products of silicon or silicon compound thin films, thin film transistors (TFT) utilizing .alpha.-Si enjoy a rapidly increasing demand in these years as a display for portable personal computers. Also, CCD is widely applied to video cameras, electronic cameras, and various optical equipment, and the demand therefor is rapidly increasing. Solar batteries using .alpha.-Si thin film as a substrate draw attention as a clean energy source because energy and resource saving problems are of great interest. On the other hand, magnetic heads and thermal heads for which the application of silicon compound thin films, especially as protective films, is expected are used especially in computer storages and output devices, and the demand therefor is also increasing. Further, research works are made on organic EL devices which are expected to find widespread applications as a self light-emitting display device, and some have been used in practice. The application of silicon compound thin films to the protective film or sealing film of organic EL devices has been investigated.
Widely used among the methods of depositing silicon or silicon compound thin films is an evaporation method using a CVD process. However, when TFT or similar products are formed using the CVD process, a film deposition rate in excess of 5 to 20 nm/min gives rise to problems including the abnormal growth of film with accompanying flakes or the damage to other films in the structure. Thus the film deposition rate is, in fact, restricted to the above-mentioned value. Since the restriction of the film deposition rate reduces mass productivity, there is a desire to have a film deposition technique capable of accommodating the recent rapidly increasing demand.